It is known that the preparation of beverages like teas, camomiles, infusions, tisanes, etc. requires to supply hot water that must be at a certain temperature for obtaining an optimal result.
For instance it is known that for a common black tea the temperature of water must be comprised, depending on the type of tea, between 85° and 100° C., that for Chinese green tea the temperature must be comprised between 80° and 90° C., that for Japanese green teas the temperature must be comprised between 75° C. and 85° C. while in the case of infusions, the temperature must be higher than that as required for the preparation of the various types of tea.
It is also known that, typically, machines for coffee preparation, for instance espresso coffee machines, comprise so-called hot water services, typically provided for by suitable devices arranged to supply hot water for the preparation of hot beverages by making direct or indirect use of a boiler comprised in the machine for generating overheated pressurised steam.
In particular, in the field of coffee machines the most common hot water supplying devices (devices) are of three types.
A first type of device provides that espresso coffee machines comprise a hot water tank and that they make use of the water therein contained, normally used for espresso coffee preparation, also for supplying the hot water service (h.w. service) by means of a suitable dispenser.
Such a type of device allows, typically, to supply hot water at temperatures comprised between 85°-95°, i.e. temperatures optimised for espresso coffee preparation but not optimised for preparation of hot beverages.
As a matter of fact, being the hot water tank provided for both, for the espresso coffee preparation and for the h.w. service supply, the two functions use the same temperature setting that, therefore, obviously, privileges the requirements for preparing espresso coffee.
Moreover, since, when the hot water service is supplied, the level of the liquid in the tank is restored by introducing cold water, very frequently the problem arises of high temperature oscillations internally to the single tank; indeed the amount of water supplied for the preparation of the beverages is very high, for instance equal or higher than half a liter of hot water in a short time, with the consequent result that the beverage preparation is negatively affected.
As a matter of fact, the thermal oscillations caused by the h.w. service supply are very heavy, if compared with those generated by the coffee supply, that for its nature provides to supply much lower amounts (50-100 cc of hot water for each coffee), and having long times of supply (15-25 second).
Such a type of h.w. service, therefore, is not very stable and not optimised to supply hot water at temperatures being optimised for the type of beverage to be prepared.
A second and a third type of device provides to use the pressurised water contained into the boiler both for the supply of overheated steam and for the supply of the hot water service, by means of a suitable dispenser.
For instance, the second type of device provides to directly use the boiler water.
In such a type of device the h.w. service is supplied at a very high temperature; therefore when the water reaches the outside of the dispenser, it partly cools down to 100° C., partly condenses and partly disperses into the atmosphere as water vapour.
Therefore the hot water supply with such a type of device, in addition to not being pleasant as it produces an actual “jet” output with spurting all around, it also involves the need for water at very high temperature which is not optimised for preparation of different hot beverages.
The third type of device provides to mix or condense in a condensation chamber the overheated and pressurised water of the boiler and cold water.
Such a type of device is for instance described in patent EP0339292B1 in the name of Applicant.
In the known device, the pressurised hot water of the boiler is mixed to a pre-determined cold water flow rate coming from a suitable duct.
In this way the “jet” of water is avoided because the condensation of the overheated steam occurs inside the device and not at the output of the dispenser.
In the known device, on the cold water duct, a “metering rod” is also provided, configured for regulating the flow of the cold water into the condensation chamber and in this way regulating the temperature of water coming out from the device (the overheated water of the boiler has a temperature of 115-140° C., depending on the regulations and on the equipment type).
In the known device it is provided that the regulation of the cold water flow is carried out mechanically, by means of a screwdriver, by rising and lowering the “rod” so as to differently throttle the cold water duct.
However such regulation possibility is very complex and difficult as it requires mechanical type operations the effect of which on temperature values of the supplied water is not easily foreseeable; due to this complexity it is provided, in practice, that the regulation of the “rod” and consequently of the hot water service temperature is carried out during installation or maintenance of the machine or device.
Therefore, a problem of said background art is that the supplying temperature of the hot water service is, typically, predetermined and that it is difficult if not impossible, when the type of beverage changes, to modify the temperature of the water upon supplying.
The Applicant has in short detected that, in view of the need for devices arranged to supply the hot water service by controlling the water temperature when the type of beverage to be prepared changes, all the known devices have the problem of not being able to allow to regulate simply and quickly, upon supplying, the temperature of the water that has to be supplied.
It is therefore clear that, desiring to meet the above demand, it is necessary to provide a device that overcomes the above stated problems of the background art.